Remote Offline install questions

I'm trying to implement a remote install on Windows Server 2012 Servers and I've got some questions:
-I copied the Windows Server 2012 prerequisites files into :\SP\2013\SharePoint\prerequisiteinstallerfiles\sxs. Is that all which is required to enable the necessary roles and Features?
-where can I define the layout of the farm (which Servers should implement which functionality: WFE, APP)? I've seen comments that this can be defined in a config.xml file but I'm not sure about the structure of that file and where this file should be stored

Thanks sadey2k
Now it is installing the .Net Framework 3.5.1 and that finishes successfully.
After that it says "Running Prerequisites Installer (offline mode) but on the machine where SharePoint should be installed I can't see the process prerequisitesinstaller.exe.
I stopped the scripts and re-run it and now I could see the prerequisitesinstaller.exe got started on that machine.

Any idea how I can get the prerequisites installed without starting the scripts a second time?

btw: what exactly shoud I copy into the Folder:
\SP\2013\SharePoint\prerequisiteinstallerfiles\sxs
(I copied all the files from the \sxs subdirectory from the Windows Server 2012 DVD but I'm assuming that I don't Need all of those files)

Thanks sadey2k
My farm right now is only a single Windows Server 2012.
It finishes installing the ".NET Framework 3.5.1" and then I get the Output "Running Prerequisite Installer (offline mode)..." but there's no Progress.
Checking the Tasks on the Server where SharePoint should be installed I see no prerequisiteinstaller.exe.
Only after stoping and re-starting the script the prerequisites are getting installed.

Is there a reboot missing after the Installation of the .NET Framework 3.5.1?